 \section{CONCLUSIONS}

The linear dynamic model of a two-stroke piston engine for small UAV applications was experimentally obtained, with low-cost sensors and a friendly, LabView-based  interface. The servo motor used to operate the carburetor's valve introduced a considerable influence on the throttle lever angle input. A user-defined model was developed in LabView and a nonlinear model for the servo motor was identified.

The instrumentation and test methodology were described and it was shown  that the model obtained has a good agreement with the experimental data.

We believe that the same test procedures could be applied to more powerful engines, installed in a proper test bed instrumented similarly.

Another objective achieved in this work was to design and use an experimental  assembly that can be boarded on a small radio-controlled plane. For a future work,  in order to a maintain a desired RPM, a PID controller can be designed and  implemented on a micro-controller. 

Combined with an indication of true airspeed,  this micro-controller could be used aboard a propeller-powered UAV to achieve and  maintain a desired thrust level. Besides that, it could be used for in-flight thrust measurements to evaluate the aircraft's overall drag.

The engine model obtained in this work is representative of the transient behaviour  of the engine in a particular condition: static thrust. Using a wind tunnel, we  believe it would be possible to repeat the same tests to determine the influence of  the airspeed in the model. 
